Opposition politicians have criticised the Welsh Government’s attempt to buyout Cardiff Airport – with the Welsh Conservatives labelling the move a waste of money.

In a heated debate in the Senedd, Shadow Transport Minister Byron Davies attacked the announcement last month by Carwyn Jones that he was seeking to buy the airport for tens of millions – with a potential £20m debt – warning that a “fantasy business model” would not be accepted by the Welsh people.

The Liberal Democrats warned that the Spanish owners of the airport had the First Minister “over a barrel” because he had announced the move before he had agreed a price.

It follows a bullish defence of the decision by Mr Jones in First Minister’s Questions on Tuesday, when he insisted the government had secured the beleaguered hub’s future.

Yesterday, Business and Enterprise Minister Edwina Hart also hit back at the criticism – indicating that the Conservatives’ dissent was rooted in ideology.

She also insisted she would not be giving a “running commentary” on progress on due diligence, which would hammer out the eventual price and conditions to the deal.

The Conservative motion expressing regret over the decision and calling for evidence to be produced on its value for money was defeated 41-12, and an amended motion was narrowly defeated 27-26.

It was the first formal debate on the deal in the chamber, after the Welsh Government announced its intention to buy the airport during the winter recess.

The move came after years of haemorrhaging passenger numbers at Cardiff, with numbers falling to 440,000 in the first half of 2012 (down from 558,000 the previous year) amid the loss of several crucial routes.

Under the government’s plans, it would buy the airport – for a price in the region of tens of millions of pounds – and would be run by a private operator on its behalf.

But the move is in the stage of exclusive due diligence negotiations with TBI, the UK airports wing of Spanish giant Abertis in which a price would be agreed.

Subject to the satisfactory completion of financial, legal and value-for-money considerations, the Welsh Government will buy the airport.

The First Minister had also defended the decision in an interview in which he said the government wouldn’t attempt to buy the airport if it were a “basket case”.

But yesterday, Liberal Democrat transport spokeswoman Eluned Parrott said the First Minister had showed his hand too early in negotiations.

She told the chamber that the airport’s Spanish owners Abertis would be shedding “precious few tears in Barcelona” over the sale, suggesting that Cardiff had merely been sold in a deal to procure the more-lucrative Luton Airport.

Ms Parrott also suggested that the First Minister’s criticism of the hub may have scared off potential buyers.

She said: “They have got the First Minister of Wales over a barrel in terms of the price, having promised to buy it before he agreed on the price.

“Until I see evidence to the contrary, I’d say that’s game, set and match to Abertis.”

Mr Davies said the government should improve infrastructure around the airport, rather than buy it based on “ideological motivations”.

He said a lack of action by the Welsh Government had “doomed the airport to an age of decline” and urged the Welsh Government to publish its business plan for buying the hub.

He said: “This decision, if it goes ahead, will be bad for Welsh taxpayers. In the long run, even worse for our only international gateway – and a financial liability we do not need in this age of austerity.

“I urge you to support this motion and prevent a catastrophic liability being placed on the public purse.

“This government is fundamentally ill-equipped to deal with the strategic direction of Wales, let alone an airport.”

But Swansea East Labour AM Mike Hedges said that Conservative AMs were behaving like “characters out of Animal Farm – private sector good, public sector bad”.

He said that when the airport was run by three county councils, it was run “exceptionally well” and delivered substantial profits, and pointed to Manchester as an example of an airport that has been successful in public control.

He said: “All we want to see is an airport which is suitable. We cannot continue with Cardiff Airport as it has been in recent years.”

Rhodri Glyn Thomas, the Plaid Cymru Member for Carmarthen East and Dinefwr, said that the First Minister had been forced to take action after months of making statements on its status.

He said that Plaid were “happy” to see services nationalised as the existing model had failed, but that there were questions over what the government was going to do if it went ahead with the purchase.

But he criticised Conservative objections to the plan, saying they were indicative that it doesn’t recognise Wales “as a nation”.

“We have to have a national airport. Every other nation has a national airport,” he said.

“In terms of the transport infrastructure between South and North Wales and between East and West Wales, that is a matter we have to develop. But we have to have a national airport.”

Responding to the debate, Ms Hart said that she was “disappointed” that ideology had gone through the debate, saying the proposed purchase was not about privatisation or nationalisation, but about Cardiff being a “gateway to Wales and the importance of economic prosperity”.

She also refused to be drawn on the details of the outline deal, saying that issues of commercial confidentiality meant she wouldn’t be giving a “running commentary” on progress.

She told AMs: “We have actually worked very closely with TBI [of which Abertis is the parent company] over many months and we’ve developed a very constructive relationship with them as a company.

“And the Welsh Government’s overriding objective has to been to secure a vibrant future for the airport.

“Nobody has been pushed into any corners, I can assure you. There hasn’t been any haste in reaching any agreement in terms of discussions with TBI.”